With the development of the information society, there has been an increase in power consumed by IT (information technology) equipment. Thus, there has been a need for a power supply system that directly receives power at a high voltage without using a power-reception transformer in order to make power supply facilities simple, and that converts the received power into a low-voltage DC voltage not greater than 100 [V] to output it.
In order to realize such a power supply system and make the power supply system smaller, a high-voltage and high-frequency insulation transformer is indispensable.
As a structure of a conventional typical high-frequency transformer, Japanese Laid-open Patent Publication No. 9-045550 discloses a structure in which a primary winding and a secondary winding are wound one over another around a shared bobbin and an insulating cover is covered to improve insulation between a ferrite core and a winding.